Extension structure



FIG. 1 is a bottom plan view of the extension structure showing my newdesign;

FIG. 2 is a side elevational view, all other side views being identicalthereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a cross sectional view taken along line 4--4 on FIG. 1.

The broken line showing of a vase and a flower is for illustrativepurposes only and forms no part of the claimed design.

The ornamental design for an extension structure, as shown anddescribed.